Hi Steve,
not wanting to talk to personaly about peoples weight, but I think Willy and Petra are fastest sloop Taipan? I don't think they are the lightest and would have guessed they are above the weight you are suggesting is optimal?
In my experience the quality of crew is more important than the weight within reason. I would be happy to sail a F16 20 kg heavier if the crew is better.
Regards Gary.